The present invention relates to a ball and socket joint. In particular, the present invention relates to a ball and socket joint having elastomeric material disposed between the socket and ball stud.
Ball and socket joints are known and are commonly used between load transmitting members which move relative to each other. Typically, ball and socket joints include a ball and stud for connection with one of the load transmitting members and a socket for connection with the other load transmitting member. The ball stud includes a ball portion which is disposed in a chamber defined by the socket. A bearing arrangement is provided between the ball portion of the ball stud and the socket to transmit forces between the ball stud and the socket and to permit relative movement therebetween.
One type of known bearing arrangement is disclosed in U.S. Pat. Nos. 2,979,353; 3,843,272; and 4,235,558. These patents disclose ball joints having elastomeric bearing material located between the ball portion of the ball stud and the socket. The elastomeric material is interposed between the ball stud and the socket and resiliently interconnects the ball stud and the socket. The elastomeric material deforms resiliently during relative movement between the ball and stud and the socket. Because the elastomeric material is resilient, it tends to urge the ball stud and socket to an original relative position once the ball stud and socket are moved relatively from the original relative position.
In these structures, the elastomeric material is bonded by a suitable adhesive to the ball portion of the ball stud to prevent slippage of the elastomeric material relative to the ball portion of the ball stud. Also, to prevent slippage of the elastomeric material relative to the socket the elastomeric material has been bonded to the socket. Such a technique is disclosed in U.S. Pat. No. 3,843,272. The bonding process, however is relatively expensive and requires frequent monitoring to assure a quality bond.
Another technique to prevent slippage of the elastomeric material relative to the socket is to substantially compress or preload the elastomeric material between the ball portion and the socket. This causes the elastomeric material to be wedged tightly against the surface of the socket. This technique has resulted in a problem that is referred to as "excess torque hysteresis." Specifically, the compression creates significant internal stresses in the elastomeric material. When the ball stud and socket are relatively moved, the internal stresses are changed. When the forces causing the relative movement of the ball stud and socket are removed, the elastomeric material will not return to its original position because the internal stresses are not the same as they were at assembly. Therefore, the ball stud and socket will not necessarily return to their original relative positions.